The World Health Organisation is warning the mosquito-borne Zika virus is “spreading explosively” and may infect up to four million people, but the chances of it reaching Malta are low. An emergency meeting will be held tomorrow in Geneva to decide how to confront the crisis, which poses a threat to unborn babies. Leonard Callus gets the lowdown on this virus.

The Aedes mosquito

The Zika virus is spread by mosquitoes of the Aedes species, a genus of mosquitoes found all over the world except Antarctica. Originally limited to tropical and subtropical zones, the species has spread as a result of human activity. Aedes mosquitoes are known vectors for numerous viral infections and apart from the Zika virus they also transmit other diseases, including dengue fever and yellow fever.

Named by the German entomologist Johann Wilhelm Meigen (1764 – 1845) who was the first to describe it in 1818, Aedes mosquitoes have noticeable black and white markings on their body and legs.

Unlike most other mosquitoes, they are active and bite only during daytime. The peak biting periods are early in the morning and in the evening before dusk. The name comes from the ancient Greek word ‘ae-de-s’, meaning odious or unpleasant.

How can the Zika cause brain damage in infants?

Experts are not certain how it happens, or even whether the virus is to blame. It was only last October that the possibility the Zika virus causes microcephaly emerged. Babies with microcephaly have unusually small heads and in most cases, the child’s brain may not develop properly during pregnancy.

Microcephaly may be triggered by German measles (also known as rubella), toxoplasmosis and alcohol consumption.

Normally, about 150 cases of microcephaly out of the three million babies born in Brazil each year are reported. Now, the Brazilian health authorities are dealing with nearly 4,000 cases. Experts say other factors may be contributing to this condition, such as simultaneous infection with other viruses, although circumstantial evidence suggests the Zika virus is the cause.

What are the symptoms of the Zika virus?

Until recently Zika was not considered a major threat as its symptoms are relatively mild, normally lasting between two to seven days after being bitten by an infected mosquito. The most common symptoms are mild fever, skin rash, aches and pains, headache, and conjunctivitis.

The symptoms usually require only rest, nourishment and other supportive care. Only one in five infected with the virus becomes ill. The virus usually remains in the blood of an infected person for about a week.

Is there a treatment?

No, there is no specific treatment or vaccine against the Zika virus. Efforts have begun to develop a vaccine but creating and testing a vaccine normally takes years and costs hundreds of millions of euros. Scientists have struggled for years to develop a dengue vaccine, related to Zika, but have not yet managed to create a viable shot so far.

The US Centre for Disease Control and Prevention has warned pregnant American women and women of childbearing age who may become pregnant to stay out of places where the virus is currently circulating.

What are the chances of the Zika virus reaching Malta?

The Zika virus is transmitted primarily by Aedes aegypti mosquitoes but can also be transmitted by Aedes albopictus mosquitoes. The Aedes aldopictus present on our shores does not carry the Zika virus. The Zika virus is not transmitted by human to human contact.

Is it less or more likely to hit us than the Ebola virus?

It is difficult to compare the risk of a threat caused by an emerging virus because they depend on a number of factors.

The risk of both is low for Europe and Malta. The mode of transmission of Zika and Ebola are different.

Are we getting ready for such a possibility? How?

Surveillance on vector borne diseases is ongoing.

Are any measures being put in place?

All doctors in Malta have been informed about this disease. Leaflets have been prepared on how to avoid being bitten by mosquitoes, while information has been released to the public.

Those who have any concerns can call the Infectious Disease Prevention and Control Unit helpline on 2132 4086.

Are measures being put in place at the airport?

No measures are required at the airport as this is not an infection that is transmitted from human to human.  You can only become infected with Zika if you travel to one of the affected countries and get bitten by an infected mosquito.

Are local travellers being warned?

Those travelling to any country affected with this virus – Barbados, Bolivia, Brazil, Cape Verde, Colombia, Dominican Republic, Ecuador, El Salvador, Fiji, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Maldives, Martinique, Mexico, New Caledonia, Panama, Paraguay, Puerto Rico, Saint Martin, Samoa, Solomon Islands, Suriname, Thailand, Venezuela and US Virgin Islands – are advised to take precautions to avoid getting bitten by mosquitoes.

It is strongly recommended that pregnant women postpone their travels to these countries.

What precautions can travellers take?

Wear clothes with long sleeves and long trousers to cover up during the day as the mosquitoes tend to be most active and bite between sunrise and sunset.

Clothing can be treated with an insecticide, like permethrin, which kills insects.

Use mosquito repellents on exposed skin areas, which have a high concentration of the active ingredient DEET. This insecticide cannot be used on infants under three months. Repellents need to be applied at regular intervals.

Those staying in accommodation without screening should sleep under a mosquito net impregnated with permethrin to avoid being bitten at night.

Pregnant women should postpone travelling to countries affected by the Zika virus. Also, travellers showing symptoms compatible with Zika, Dengue or Chikungunya virus disease within three weeks from returning from an affected area should contact their GP.

What is the major concern?

While the symptoms are mild, the major concern at the moment is that there seems to be evidence suggesting that pregnant women infected with the Zika virus could give birth to babies with an unusually small head – a condition called microcephaly.

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The virus was isolated in April 1947 from a feverish monkey that had been placed in a cage in the Zika forest of Uganda.

Investigations of mosquitoes initiated in 1946 as part of the study of human yellow fever at the Yellow Fever Research Institute in this forest.

The transmissible agent from the monkey’s serum was first described as the Zika virus in 1952 and was isolated for the first time from humans in Nigeria in 1968.

By 1981, evidence of human infection was reported from other African and Asian countries.

The first outbreak in the Pacific was in Micronesia in 2007 and there have since been large outbreaks in four other Pacific island nations.

The situation became dramatically different when Zika arrived in the Americas, where it is now spreading explosively.

The virus is still a bit of a puzzle. Having been identified almost 70 years ago, why did it start spreading among humans only recently? One possibility is that the virus has evolved, either making humans more susceptible or making it easier for mosquitoes to transmit it.

The virus is known to be present in 23 countries across Africa, the Americas, Asia and the Pacific.

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1947
The virus was discovered in 1947 in a feverish rhesus macaque monkey living in the Zika Forest near Lake Victoria in Uganda by the scientists of the Yellow Fever Research Institute. Until 2007 scientists knew of only 14 human cases of the disease.

2007
Yap Island in the southwestern Pacific Ocean: within a few months, nearly 75 per cent of the island’s 11,000 residents older than three were infected. Initially, those sick with Zika developed fever, joint pains and eye inflammation; then a red, bump like rash erupted, sometimes followed by painful swelling of hands and feet. Some people vomited. Others were sensitive to light. But the symptoms usually resolved a couple of days later, and no one died.

2013
Zika popped up in Tahiti and other parts of French Polynesia. An estimated 11 per cent of the population of these islands (28,000 persons) sought medical care after contracting the virus.

2014
The Zika virus appeared in New Caledonia, east of Australia, Cook Islands and Easter Island.

2015
Since May, Brazil has faced an unprecedented number of Zika virus cases, more than one million. The Brazilian Health Ministry has said 80 per cent of those who catch Zika have shown no symptoms. The rest may suffer fever, muscle pain and rashes for a few days, and most people recover quickly. An unprecedented number of microcephaly cases has been registered.

2016
In Colombia, Ecuador, El Salvador, and Jamaica the authorities issued recommendations to avoid pregnancy for eight months.